An enormous queue of taxis is seen waiting to fill up their tanks at a natural gas at a station Taiyuan, capital of northern China's Shanxi Province.

Due to rising petrol costs, some Chinese cities have been converted their taxi fleet to run on natural gas.

However, due to a current lack of gas stations where they can fill up, drivers are often forced to queue for hours. One driver said that he spends three to four hours each day waiting to get fuel.

Round the block: Taxis in Taiyuan, China, are forced to queue for hours for natural gas as demand, driven by high petrol prices, skyrocket

Queue: Half of China's one million taxis are now gas-powered but supply hasn't kept up with demand

Rigmarole: One driver said that he spends three to four hours each day waiting to get fuel

Natural gas fuel combustion produces significantly less harmful emissions than petrol and in 1999 Chinese authorities set a 10 per cent target for clean vehicles as a portion of the overall vehicle population.

According to Forbes (LINK), the total number of taxis in China is more than 1.1 million, half of which have gas engines.